Considering a seismic data acquisition process and system and looking to FIG. 1, a seismic data acquisition system 100 includes a vessel 102 towing a plurality of streamers 104 that can, for example, extend one or more kilometers behind the vessel 102. Each of the streamers 104 can include one or more “birds” 106 that maintain the streamer 104 in a known fixed position relative to other streamers 104. Further, the one or more “birds” 106 are capable of moving the streamers 104 as desired according to bi-directional communications received by the birds 106 from the vessel 102.
One or more source arrays 108 can also be towed by vessel 102, or by another vessel (not shown), for generating seismic waves. Source arrays 108 can be placed either in front of or behind the receivers 112 (only one representative receiver being illustrated per streamer), or both behind and in front of the receivers 112. The seismic waves generated by the source arrays 108 propagate downward, reflect off of, and penetrate the seafloor, wherein the refracted waves eventually are reflected by one or more reflecting structures (not shown in FIG. 1) back to the surface of the sea. The reflected seismic waves then propagate upward and are detected by the receivers 112 disposed on the streamers 104. The seismic waves then reflect off of the free surface, i.e., the surface of the sea, traveling downward and are once again detected by the receivers 112 disposed on streamers 104 as receiver ghosts. This process is generally referred to as “shooting” a particular seafloor area, with the seafloor area referred to as a “cell” and the sea surface referred to as a “free surface.”
Conducting a seismic survey is a complicated and expensive operation. As described above, large vessels are involved with complicated maneuvers associated with towing a series of streamers and source arrays, and turning the vessel to make numerous passes through an acquisition area. Further, other vessels can be involved for towing additional source arrays, and it may be necessary to coordinate the travel paths of the entire fleet of vessels. Completing a seismic survey is a function of following a predetermined plan of maneuvers across a large predetermined area of the sea. One way to decrease the time required to complete a seismic survey is to tow a larger number of streamers, corresponding to a larger area of coverage by the streamers, across the predetermined seismic survey area, and then reducing the number of passes.
However, while performing the survey, operational issues can arise such as broken or tangled lines, failed receivers, failed source arrays, etc., wherein the greater complexity of more streamers increases the probability of problems associated with completing the survey. In another aspect, the greater the complexity of the equipment, usually reflected by a larger number of streamers connected to a vessel, the greater the risk of injury to the personnel operating the seismic survey equipment because of the inherent danger of proximity to the operating seismic survey equipment. Additionally, using a large number of streamers may add significant expense as the streamers are themselves quite expensive. Accordingly, it would be desirable to avoid the afore-described problems and drawbacks, and provide systems and methods that collect the required amount of seismic data with a reduced number of streamers and/or in a smaller amount of time.